Photogrammetric projection apparatus



ym-203m 56 37 P 1959 c. H. BRUMLEY 2,901,941

PHOTOGRAMMETRIC PROJECTION APPARATUS Filed May 20, 1957 3 Sheets-Sheet 1 IN V EN TOR.

CORWIN H. BRUMLEY ATTORNEYS p 1, 1959 c. H. BRUMLEY 2,901,941

PHOTOGRAMMETRIC PROJECTION APPARATUS Filed May 20, 1957 3 Sheets-Sheet 2 g FIG. 5

AMPLIFIER t: AMPLIFIER N440 INVENTOR- CORWIN H. B RUM LEY BY Q 54% ATTORNEYS Sept. 1, 1959 c. H. BRUMLEY 2,991,941

PHOTOGRALMETRIC PROJECTION APPARATUS Filed May 20, 1957 s Sheets-Sheet 3 LlNE I 54 55% Ha? VOLT P M NO TH #96 LAQP P 6.8 G 5 LIG HT INTENSITY FIG. 9

ERROR j SIGNAL IN VEN TOR.

CoRwm H.BRUM LEY ATTORNEYS United States Patent PHOTOGRAMMETRIC PROJECTION APPARATUS Corwin H. Brumley, Penfield, N.Y., assignor to Bausch & Lomb Optical Company, Rochester, N.Y., a corporation of New York Application May 20, 1957, Serial No. 660,392

Claims. (CI. 88-24) This invention relates to photogrammetic devices, and more particularly to a tracking system for continuously and automatically orienting the optical axis of one or more of the illuminators of the stereoscopic projection apparatus with respect to a movable plotting table used in conjunction therewith.

Generally, in apparatus of this character, the illuminator for each projector is adapted to rotate on two axes located generally in a single plane and at 90 to each other thus permitting scanning movement of the light beam for the full dimension of a worktable carrying a sheet upon which a map is to be drawn. A plotting or tracing table is utilized for tracing data on the map and in doing so, the table is placed upon the worktable and moved thereabout to trace the various portions of the map which are projected onto the platen of the table. It is highly desirable, in so moving the plotting table, that the movements of the illuminators for the projection apparatus are at all times in synchronism with the movements of the plotting table. To accomplish this cooperation between the movements of the plotting table and the illuminators, it has been proposed to use a number of telescoping rods which are connected between the table and the illuminator for each of the projectors so that upon movement of the plotting table about the worktable the illuminators are correspondingly moved to follow the plotting table so that the images are pro jected thereupon.

The use of such telescoping rods has introduced numerous disadvantages, the most notable being that the rods themselves are rather cumbersome to manipulate requiring continual connecting and disconnecting of the rods when the removal of the plotting table is desired. In addition, the rods seriously limit freedom of movement of the operators hands around the plotting table and care must be exercised in order to prevent inadvertent bending or twisting of the rods. Generally too, the full extension of the rods is relatively short thus restricting movement of the plotting table about the worktable. In the event the operator desires to change maps, he must disconnect the rods in order to move the plotting table on another support while the map is being changed.

The present invention overcomes these disadvantages by eliminating all mechanical linkage between the plotting table and the illuminators and to this end there is provided a motor system for rotating the illuminators about two coordinate axes in response to movement of the plotting table. A lighting system is arranged on the platen of the plotting table and a sensing device, associated with the illuminator mounting gimbals, is adapted to respond to the positioning of the lighting system for directing the optical axes of the illuminators substantially onto the center part of the platen for all movements of the plotting table. The response of the directing move ment of the projection axis is continuous and automatic and is capable of being sensitized in that any movement of the platen in a horizontal plane will immediately result in a corresponding movement of the illuminators to follow the platen.

It is the principal object of the present invention to provide a tracking system which will continuously and automatically motivate a projector illuminator mechanism for following a screen or platen in accordance with the movement thereof.

Another object of the present invention is to eliminate cumbersome mechanical connections between a plotting table and the projection illuminator mechanism of a photogrammetric apparatus.

Other objects and advantages will become apparent from the following description taken in conjunction with the drawings wherein:

Fig. 1 is a perspective view of a portion of a photogrammetic apparatus showing the present invention applied thereto;

Fig. 2 is a side elevational view of a detail of one of the projectors shown in Fig. 1;

Fig. 3 is a diagram showing an electronic circuit adapted to be influenced by the phase relationship and intensities of the light sources associated with the platen;

Figs. 4 and 5 represent the varying relationship of the light sources as viewed by the sensing element under varying conditions;

Fig. 6 represents curves showing the relationship of the line voltage and the energizing voltages for each of the light sources;

Fig. 7 represents a curve for the error signal resulting from the total efiect of the light sources upon the sensing element for one condition of operation;

Fig. 8 represents curves showing the relationship of the intensities of each of the light sources in another condition of operation;

Fig. 9 represents a curve for the error signal resulting from the total efiect of the light sources upon the sensing element for another condition of operation;

Fig. 10 is a sectional view of a modification of an element which can be used in the apparatus shown in Fig. 3; and

Figs. 11 and 12 represent varying relationships of the element shown in Fig. 10 as viewed by the sensing element under varying conditions.

The present invention is adapted to be associated or incorporated in the projection system of a conventional photogrammetric stereomapping apparatus, an example of which is illustrated in Fig. 1 and designated generally by the reference numeral 10.

The apparatus 10 and the components thereof may be of any suitable or conventional construction except for certain components thereof which will be modified for purposes of the present invention. The apparatus 10 includes a pair of suitable projection units generally designated by the reference numerals 12, 14. As is known in the art, the light rays from each of the projectors 12, 14 pass through an optical system which includes a red or blue filter, a diapositive of an aerial photograph being projected and a suitable lens for projecting a red or blue image as the case may be of the photograph. Both images are projected upon the platen 18 of a plotting or tracing table 20 which can be moved about the table 16. The optical axis of each of the projectors 12, 14 is in alignment with the center point 22 of the platen 18 and as the tracing table 20 is moved about the worktable 16, the illuminating devices for each of the prothe platen 18, 90 apart. For purposes of later description, it will be assumed that each of the lamps corresponds to a point on the compass, that is, the lamps 24, 26, 28, 30 will correspond with the North, East, South, and West points of the compass, respectively. The lamps are arranged equidistant from the point 22 and are preferably located in recessed portions of the platen in order to eliminate any unnecessary projections on the surface of the platen. Suitable conductors 32 are connected to the lamps 24-30 for conveying electrical energy to the lamps from a source to be described hereinafter.

The photogrammetric apparatus is provided with a frame structure 34 (only one of which is shown) mounted on suitable adjustable screws 36 which in turn are supported on the frame of the worktable 16. A horizontally disposed cross bar 38 is supported upon the top of the frame structure 34 and horizontally spaced and slidably mounted on the cross bar are a pair of arm structures 40 (only one shown in Fig. 1) for supporting the projectors 12, 14 above the worktable 16. As is customary in photogrammetric apparatus of this type, the projectors of the platen, means are provided for permitting universal pivotal movement of the illumination devices. To this end, the illumination device 42 is mounted on the upper end of vertically disposed bow-shaped arm 46 while the lower end of the arm 46 is pivotally mounted by a pivot 48 to the bight portion of a gimbal yoke 50. The ends of the gimbal yoke 50, in turn, are pivotally mounted, on pivots 52, to the adjacent ends of a U-shaped bracket 54 extending from the arm structure 40. Similarly, the illumination device 44 is mounted on the upper end of a bow-shaped arm 56 pivotally connected at 58 to the bight portion of the gimbal yoke 60 which, in turn, is pivotally connected to the arm structure 40 associated with the projector 14. It will be apparent to those skilled in the art that the pivotal arrangement of the gimbal yokes 50 and 60 with respect to the arm structure 40 and the pivotal connections of the arms 46, 56 relative to their respective gimbal yokes will permit universal movement of the illumination devices and, consequently, result in the scanning of the images of the photographs-to-beprojected over a substantial area of the worktable 16.

As previously stated, the projectors 12 and 14 may be of any conventional type and for purposes of this invention, various modifications of the conventional projectors, so far described, have been made in order to implement the present invention. Since the projectors 12 and 14 are duplicates, the modification incorporated in only one of these projectors will now be described. It will be understood that the same modification will apply to the other projector as will hereinafter be described in reference to the electric circuitry of the invention.

Adjacent the lower end of the arm 46, there is mounted a phase sensitive electric motor 62 which has a suitable drive gear (not shown) connected to the shaft (not shown) of the motor and in mesh engagement with a sector gear 64 secured adjacent the bight portion of the gimbal yoke 50. Upon rotation of the drive gear in either direction of rotation, the same will walk along the stationary sector gear 64 for causing rotation of the arm 46 about the pivot 48. A similar phase sensitive or servo electric motor 66 is mounted on one of the ends of the gimbal yoke 50 and is provided with a drive gear 68 (see Fig. 2) which is in mesh engagement with a sector gear 70 secured to the bracket 54. Upon rotation of the gear 68 in either direction the same will walk on the sector gear 70 and permit rotation of the gimbal yoke 50, and consequently the illumination device 42, about the pivotal axis 52. Similar motors and sector gears are associated with the arm 56 and the gimbal yoke 60 for imparting the same universal movement to the illumination device 44 and since these structures are essentially duplicate, further description of the structure thereof will be unnecessary.

The electrical circuitry and the remaining mechanical structure of the present invention will now be described. In Fig. 3, the four lamps 24, 26, 28, 30, respectively designated the North, East, South, West lamps, and associated with the tracing table 20, are shown connected to a power supply comprising a transformer 72, a capacitor 74, a resistor 75 and rectifiers 76, 78, 80, 82 connected to the lamps, respectively. The power supply connections are such as to energize the lamps with a half-wave rectified line voltage of 115 v, at 60 cycles. As shown in Fig. 6, the phase of the energizing voltage to each lamp is shifted with respect to each adjacent lamp, for example, with curve 84 representing line voltage and curve 86 representing the energizing voltage of the South lamp, the voltage of the West lamp, represented by curve 88, is 90 out of phase with respect to the energizing voltage for the South lamp; the voltage of the North lamp, represented by the curve 90, is 90 out of phase with respect to the voltage for the West lamp; and the voltage of the East lamp, represented by the curve 92, is 90 out of phase with respect to the voltage for the North lamp.

The lamps may be of any conventional type and for purposes of this invention the General Electric #327 type lamps were used. As characteristic of all lamps, there is a slight thermal time constant associated with each of the lamps used in the present invention as will be seen in the drawings. The light intensity for each of the lamps is shown in Fig. 8 wherein: numeral 94 denotes the South lamp intensity, 96 denotes the North lamp intensity, 98 denotes the West lamp intensity, and 100 denotes the East lamp intensity. As seen in Fig. 8, the thermal time constant for each of the lamps has been illustrated; however, this has negligible effect in the operation of the present invention since, it will be noticed, each of the lamps contains a strong component of modulation at the power supply frequency, namely, 60 cycles.

As will presently be described in more detail, the images of the four lamps 24, 26, 28, 30 and the platen 18 are adapted to be viewed through a sight tube 102 mounted on a support 104 extending from the end of the arm 46 (see Fig. 1). The axis of the sight tube 102 is in coincidence or near coincidence with the optical axis of the projector 12 and as we shall presently see, the purpose of the motors 62, 66 is to continually and automatically direct the axis of the tube 102 and the axis of the illumination device 42 so that the same are in alignment with the center point 22 on the platen 18 as the latter is moved about the worktable 16. A similar tube 106 is associated with the projector 14 and its axis is in coincidence or near coincidence with the optical axis of the projector 14; both axes being directed so that they continuously and automatically remain on the point 22. Each of the lamps 24, 26, 28, 30 are provided with a red filter for blocking or absorbing distracting visible light and permitting the passage of infrared light.

In Fig. 3, the sight tubes 102, 106 are shown in a position with respect to the four lamps for focusing the images thereof on a pair of lead sulphide detectors 108, 110, respectively. Each of the sight tubes (only sight tube 102 will be described) comprises a variable density filter 112 at the end thereof which receives the image forming light rays from the lamps and a focusing element 114 at the other end. An infrared filter 116 may be interposed between the filter 112 and element 116 for insuring the filtering out of all but the infrared light to which the lead sulphide detectors 108, are most sensitive. As shown in Figs. 4 and S, the variable density filter 112 is of circular symmetry, clear in the center and gradually becoming denser near the periphery. Figs. 4 and 5 show the platen 18 and the lamps as viewed through the sight tubes 102, 106 by the sensing areas of the detectors, the numeral 118 indicating the edge of the platen and the numeral 120 indicating the edge of the field of view. It will be noted in Fig. 4, that the images of the lamps fall upon portions of the filter 112 having equal density whereas, in Fig. 5, the South lamp image falls in a more dense portion than the North lamp image. As will be presently described, in the former case, the electrical system for the present invention is balanced with axes of the illumination devices and the sight tubes in line with the point 22 of the platen.

In Fig. 3, the detector 108 is shown as being connected to the input terminals 120 of an amplifier 122 which serves to amplify a signal generated by the detector and has its output terminals 124 connected to the signal windings 126, 128 of the motors 62, 66, respectively. As shown, the windings 126 and 128 are connected in parallel and the winding 128 has a capacitor 130 connected between one of its ends and one of the output terminals 124. The motors 62, 66 are also provided with field windings 132, 134, respectively, and these are connected in parallel and to a suitable source of alternating current 136 of 11-5 v. at 60 cycles. As previously stated, the motors 62 and 66 are of the servo type wherein the motor shaft will rotate only when the phase of the current in the signal winding is in quadrature with the field winding. If the current in the signal winding is in phase with or 180 out of phase with the field winding the motor shaft will not rotate. Another characteristic of this type of motor is that the frequency of the signal voltage on the signal winding must be the same as the frequency of the field winding voltage or at least the signal voltage must have a frequency component of the frequency of the field winding voltage.

Similarly, the detector 110 is connected to the input terminals 138 of an amplifier 140 which has its output terminals 142 connected to the signal windings 144, 146 of servo motors 148, 150, respectively. The motor 148 is associated with the arm 56 and the gimbal ring 60 of the projector 14 in exactly the same manner and for the same purpose as the motor 62 for the projector 12. Similarly, the motor 150 performs the same function for the projector 14 as the motor 66 performs for the projector 12. The motors 148, 150 are provided with field windings 152, 154, respectively, and these are connected in parallel and to the source 136. There is a capacitor 155 connected between one end of the winding 144 and one of the output terminals 142 of the amplifier 140.

When the line through the axis of the sight tube 102 is in coincidence with the center point 22 of the platen 18, the electrical system is in balance, that is, the motors 62, 66, 148, 150 are deenergized and the lead sulphide detector 102 will see all four lamps 24, 26, 28, 30 at equal intensity, as shown in Fig. 4. With these intensities equal, the electrical error signal produced by the detector will be a summation of the signals generated by the light falling thereon from each of the lamps viewed. The error signal generated by the detector is shown by the curve 156 in Fig. 7 wherein, it is noted, the signal contains no 60 cycle component. Consequently, the error signal upon reaching the signal windings 126, 128, will have no effect on the motors 62, 66, respectively, since the motors are sensitive only to 60 cycles. In this condition, the electrical system is in balance and the line through the axis of the illumination device 42 is in coincidence with the center point 22.

Since the electronic circuit associated with the sight tube 106 and the projector 14 is similar in all operating respects to the circuit associated with the sight tube 102, the former circuit will likewise be in balance when the line through the axis of the tube 106 is in coincidence with the point 22 of the platen 18.

Assuming now that the tracing table 20 is moved slightly to the south, the detectors 108, will see the North lamp at greater intensity than the South lamp. The East and West lamps will still be of equal intensities as shown in Fig. 5. The net 60 cycle signal generated by the detectors 102, 106, and indicated by the numeral 156 in Fig. 9, will be 180 from line phase and in the form shown, will activate the North-South motors 66 and for directing the axes of the sight tubes 102, 106 and the illumination devices 42, 44, respectively, into coincidence with the center point 22 of the platen 18. The same signal, that is, the error signal 156, is fed to the East-West motors 62, 148 but only after being shifted 90 by the capacitor 130, and since this resulting signal is in quadrature with the line voltage, the East-West motors 62, 148 will remain at rest.

In the event the tracing table 20 is displaced in an east-west direction, the resulting error signal will have a 60 cycle component in quadrature with the line voltage and in the form shown would have no effect on the North- South motors 66, 150. The same signal will be shifted by the condensers 130, back to line phase and would set the East-West motors 62, 148 into operation.

In the embodiment of Figs. 10-12, a modification of the sight tubes 102, 106 is shown and this comprises a tube 160 closed at one end for supporting a lead sulphide detector 162 thereat. The detector 162 is adapted to receive light through an aperture 164 formed in a diaphragm wall 166 at the other end of the tube, and a series of diaphragm partitions 168 are interposed between the end diaphragm 166 and the detector 162, each of the diaphragm partitions being formed with apertures 170 which become progressively smaller as they approach the detector. The image of the platen 18 and the lamps, as viewed by detector 162, is shown in Fig. 11 where the electrical system is in balance and in Fig. 12 where the tracing table has been displaced to the south, and in this regard Figs. 11 and 12 are similar to Figs. 4 and 5, respectively. In Fig. 11, the edges of the apertures 164, 166, as designated by the reference numeral 172, are shown fully encompassing all of the lamps 24, 26, 28, 30 at approximately the same distance from the edges 172. Consequently, the light from each of the lamps will fall upon the detector 162 with equal intensity, however, in the event the tracing table is displaced to the south, the South lamp 28 will be covered somewhat, depending upon the amount of movement, by the diaphragms 166, 168. Upon this occurrence, the North-South motors 66, 150 will become energized to direct the axes of the sight tubes and illumination devices in coincidence with the center of the platen whereupon the electric system once again will be in balance. It will be noted that in the embodiment of Figs. 10-12, there is no variable density filter associated with the tube 160. The equivalent effect is accomplished by the partial or total covering of the particular lamp or lamps concerned by the edges of the various diaphragms. Y

A pair of the sight tubes 160 may be substituted for the tubes 102, 106 shown in Fig. 3 and the detector 162 may be detached from the tube 160 as is the case for the tubes 102, 106 as long as the detector is adapted to see the platen in the manner previously described in reference to Figs. 11 and 12. Conversely, the optical system comprising the filters 112, 116 and the lens 114 may be incorporated in a tube similar to tube 160 with the detector 108, or 110, as the case may be, mounted within the tube.

The present invention may have use in other apparatus wherein it is desired to track an object for any number of purposes. While there is disclosed a signal source comprising four lamps, any other number may be utilized to effect similar results. It will be also obvious to those skilled in the art that any number of tracking devices may be employed and while only two of these devices 7 have been described, the invention is not limited to such number.

From the foregoing description, it will be appreciated that the present invention provides means for continuously and automatically directing the optical axes of the individual illurninators of a stereoscopic photogramrnetric instrument upon a tracing table, thus eliminating the need for connecting rods between the table and the projectors. The response of the electrical system and consequently the correction or movement of the illuminators to follow the tracing table for each movement thereof is practically instantaneous.

While there is in this application specifically described one form and a modification of a part thereof which the invention may assume in practice, it will be understood that this form is shown for purposes of illustration, and that the same may be modified and embodied in various other forms or employed in other uses without departing from the spirit or the scope of the appended claims.

I claim:

1. In a stereoscopic projection instrument for use in making maps from photographs, the combination comprising an illumination device, means for mounting said illumination device for universal movement, a movable tracing table having a platen, a source of a modulated signal carried by said tracing table, said signal source including a plurality of individual sources of light, each of said individual sources of light having a radiant energy output of a predetermined phase sense and magnitude, said modulated signal being a composite of said individual sources of light, radiation sensitive means adapted to receive said modulated signal for generating a second signal having a wave form corresponding to the wave form of said modulated signal reaching said sensitive means, means responsive to said second signal for dirccting an axis of said illumination device to follow said tracing table in accordance with the deviation of said wave form of said modulated signal reaching said sensitive means from said wave form of said modulated signal, and means for varying the wave form of said modulated signal reaching said sensitive means in accordance with movements of said tracing table.

2. In a stereoscopic projection instrument for use in making maps from photographs, the combination comprising an illumination device, means for mounting said illumination device for universal movement, a movable tracing table having a platen, a source of a modulated signal carried by said tracing table, said signal source including a plurality of individual sources of light, each of said individual sources of light having a radiant energy output of a predetermined phase sense and magnitude, said modulated signal being a composite of said individual sources of light, radiation sensitive means adapted to receive said modulated signal for generating a second signal having a wave form corresponding to the wave form of said modulated signal reaching said sensitive means, means responsive to said second signal for directing an axis of said illumination device to follow said tracing table in accordance with the deviation of said wave form of said modulated signal reaching said sensitive means from said wave form of said modulated signal, and means for varying the wave form of said modulated signal reaching said sensitive means in accordance with movements of said tracing table, said lastnamed means including a filter having a relatively low density portion in the center thereof and progressively denser portions as the radial distance from said center portion increases for modifying said wave form of said modulated signal reaching said sensitive means in proportion to the movement of said tracing table.

3. In a stereoscopic projection instrument for use in making maps from photographs, the combination comprising an illumination device, means for mounting said illumination device for universal movement, a movulated signal carried by said tracing table, said signal source including a plurality of individual sources of light, each of said individual sources of light having a radiant energy output of a predetermined phase sense and magnitude, said modulated signal being a composite of said individual sources of light, radiation sensitive means adapted to receive said modulated signal for generating a second signal having a wave form corresponding to the wave form of said modulated signal reaching said sensitive means, means responsive to said second signal for directing an axis of said illumination device to follow said tracing table in accordance with the deviation of said wave form of said modulated signal reaching said sensitive means from said wave form of said modulated signal, and means for varying the wave form of said modulated signal reaching said sensitive means in accordance with movements of said tracing table, said last-named means including a diaphragm formed with an aperture through which the said modulated signal is adapted to radiate before reaching said sensitive means whereby movements of said tracing table will permit the edge of said aperture to modify the said modulated signal passing therethrough.

4. In a stereoscopic projection instrument for use in making maps from photographs, the combination comprising an illumination device, means for mounting said illumination device for universal movement, a movable tracing table having a platen, a source of a modulated signal carried by said tracing table, said signal source having a radiant energy output of a predetermined phase sense and magnitude, radiation sensitive means adapted to receive said energy output for generating a second signal having a phase sense and magnitude proportional respectively to the phase sense and magnitude of the radiant energy reaching said sensitive means, means responsive to said second signal for directing an axis of said illumination device in one direction to follow movement of said tracing table in said one direction in accordance with a first phase sense and magnitude of said modulated signal reaching said sensitive means and in another direction to follow movement of said tracing table in said other direction in accordance with a second phase sense and magnitude of said modulated signal reaching said sensitive means, and means for varying the wave form of said modulated signal reaching said sensitive means between said first phase sense and magnitude and said second phase sense and magnitude in accordance with movements of said tracing table.

5. In a stereoscopic projection instrument for use in making maps from photographs, the combination comprising an illumination device, means for mounting said illumination device for universal movement, a movable tracing table having a platen, a source of a modulated signal carried by said tracing table, said signal source including four individual sources of light spaced from each other with respect to the center point of said platen, each of said individual sources of light having a radiant energy output of a predetermined phase sense and magnitude, said modulated signal being a composite of said individual source of light, radiation sensitive means adapted to receive said modulated signal for generating a second signal having a wave form corresponding to the wave form of said modulated signal reaching said sensitive means, means responsive to said second signal for directing an axis of said illumination device in one direction to follow movement of said tracing table in said one direction in accordance with a first phase sense and magnitude of said modulated signal reaching said sensitive means and in another direction to follow movement of said tracing table in said other direction in accordance with a second phase sense and magnitude of said modulated signal reaching said senable tracing table having a platen, a source of a mod- 7& fiitive means, and means for varying the wave form of References Cited in the file of this patent UNITED STATES PATENTS 2,417,446 Reynolds Mar. 18, 1947 10 Kelsh Oct. 1 1948 Herbold Dec. 27, 1949 Kelsh Dec. 27, 1949 Linderman Ian. 17, 1950 Herbold Dec. 5, 1950 Kelsh May 15, 1951 Falkenstein Aug. 21, 1951 Menzel July 22, 1952 Knapik May 18, 1954 

